System and method for the wireless signal transmission for checking probes

ABSTRACT

A system for numerical control machine tools comprises contact detecting probes, powered by a battery, that transmit radio-frequency signals to associated interfaces. When the probes are not being utilized for checking cycles, they are in a low-energy consumption state, in other words the circuits of the probes are only partially powered. When the need arises, the circuits of a probe are fully powered by the battery, by a radio-frequency activation signal. The procedure for activating a selected probe includes the sending of a generic activation signal from the associated interface, the transmitting of an identification signal from all the probes that have been activated by the generic signal and the sending of a generic confirmation signal from the interface in reply to the identification signal of the selected probe.

The application claims the benefit of PCT Application Ser. No.PCT/EP96/01874, filed May 6, 1996.

TECHNICAL FIELD

The invention relates to a system comprising a plurality of assemblieswith detecting devices, transmitting devices for the wirelesstransmission of signals, including means for generating and sendingidentification signals, receiving devices for the wireless reception ofan activation signal for activating the assemblies, power supply means,and switching means adapted for providing connection between the powersupply means and the transmitting devices, and at least a control unit,physically remote from the assemblies, with means for generating andtransmitting the activation signal, means for receiving theidentification signal, and means for generating and transmitting to theassemblies a confirmation signal, the receiving device being apt forreceiving said confirmation signal. The invention also relates to amethod for controlling the activation of a remote assembly by a controlunit in a system with at least one control unit and a plurality ofassemblies, physically remote from the control unit and comprising powersupply means, detecting devices, receiving devices and transmittingdevices for receiving and transmitting wireless signals, the methodcomprising the following steps: generating and sending an activationsignal by the control unit, receiving said activation signal by thereceiving devices of at least a part of said plurality of assemblies,temporary energizing the assemblies of said part further to saidreception, sending, by the transmitting devices of the assembliesbelonging to said part, associated identification signals at instantssubsequent to said temporary energizing, receiving the identificationsignals by the control unit, sending, by the control unit, aconfirmation signal upon reception of one of the identification signals,and interrupting the temporary energizing of each assembly that does notreceive the confirmation signal subsequently to the sending of theassociated identification signal.

BACKGROUND ART

There are known measuring systems as, for example, systems in numericalcontrol machine tools for detecting the position and/or the dimensionsof workpieces, by checking heads, or contact detecting probes mounted inthe machine, that in the course of the checking cycles displace withrespect to the workpiece, touch the surface to be checked and, aftercontact has occurred, cause the wireless transmission of signals toreceiving units.

Each receiving unit is in turn connected, by means of an interface unit,to a relevant numerical control unit that, by processing other signalsindicative of the position of the probe, receives information about theposition of the workpiece surfaces.

The probes can include electric batteries for the power supply of thecircuits detecting contact and the transmission devices. The wirelesstransmission can occur, for example, by emitting electromagnetic signalsof optical or radio-frequency type.

Since a probe is utilized just for short time intervals during themachining cycle of its machine tool, it is normally kept in a "stand-by"condition of low power consumption and it is powered up only when thereis the need to perform a checking cycle.

The switching from the "stand-by" condition to the "powered-up" statecan be carried out by controlling suitable switching devices on theprobe by means of wireless activation signals sent by the receivingunit.

A system of this type is illustrated and described in U.S. Pat. No.4,693,110.

In a working environment, for example in a workshop, there can bemultiple checking probes, installed in various machine tools: eachmachine tool can comprise, in general, one or more probes for performingchecking cycles and sending associated signals to the receiving unit ofthat machine. Generally, for each machine tool just a probe at a time isselected to perform a checking cycle, even though there are cases inwhich, in specific machines, two (or, in theory, more) probes performcheckings in partially coincident moments.

When an activation signal is sent by the interface of a machine forenergizing a specific probe in the machine that has to perform achecking cycle, it is advisable to avoid that other probes in thatmachine or in adjacent machines be concurrently activated.

The need to activate an individual probe and not others operating in thesame environment is particularly evident when transmission between theprobe and the receiving unit occurs (in both ways) by means ofradio-frequency modulated signals, as in this case, unlike to whatoccurs, for example, in optical-type transmissions, it is practicallyimpossible to assign a precise direction to the emitted radiation, and asingle activation signal "awakes" all the probes in a specific workingarea.

A radio telemetry system in which a master station activates a pluralityof transponders is disclosed by EP-A-0428322. In the system thereindescribed, the transponders are meters and the master station, that ismovable, has to collect the data reported from all of them, one by one,and does so, awaking them from a stand-by state, in a substantiallyrandom order. In fact, the order depends on different circumstancesoccurring at the moment the awaking action starts (e.g.: which of anumber of radio channels is the quietest; which of the meters islistening on that channel; which of the awoke meters is the nearest tothe movable station; . . . ).

As a consequence, the system shown in EP-A-0428322 cannot be used in ameasuring system in which a selected, specific probe has to beactivated.

DISCLOSURE OF THE INVENTION

Object of the present invention is to provide a system and a method forthe wireless transmission of electromagnetic signals between checkingprobes and remote receiving units, that enables to activate, in a simpleand inexpensive way, an individual probe among a plurality of probesoperating in a specific environment.

This object is achieved by a system and an associated method, accordingto claims 1 and 7.

An advantage that a system and a method according to the inventionprovide consists in the possibility of utilizing, on the probe, a verysimple and low-consumption receiver; this advantage becomes ofconsiderable importance in the case of radio-frequency signaltransmission.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is hereinafter described in more detailwith reference to the enclosed sheets of drawings, given by way of nonlimiting example only, wherein

FIG. 1 shows, in simplified form, the probes and the interface devicesof a plurality of machine tools installed in a specific workingenvironment,

FIG. 2 is a block diagram of a transceiver section an interface device,

FIG. 3 is a block diagram of a transceiver section a probe,

FIG. 4 is a block diagram indicating the functions according to a methodof the invention, and

FIG. 5 is a diagram showing the signals exchanged between the probes andan interface device in a system according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates, in simplified form, three machine tools (forexample, lathes and/or machining centers) M1, M2 and M3, located in asame working area, with associated numerical controls N1, N2, N3, andinterface devices I1, I2 and I3.

Some checking probes, more specifically contact detecting probes, areinstalled on M1 (S1a, S1b, S1c and S1d), M2 (S2a and S2b) and M3 (S3a,S3b and S3c), physically remote from the relevant interface devices I1,I2 and I3.

Each probe comprises known detecting devices, in particular switchingdevices. With reference to FIG. 1, these devices have been schematicallyshown and identified, for the sake of simplicity, with reference number38 specifically just for probe S1a. The interface devices and the probescomprise radio-frequency receiving and transmitting devices, shown inFIGS. 2 and 3, for receiving and transmitting wireless signals.

In particular, a control unit of the interface device shown in FIG. 2,for example, I1, comprises a logic unit 1, for generating activation andenable signals, coupled to numerical control N1 of machine M1, aradio-frequency oscillator 3 and a modulator 2, connected to each otherand to unit 1, a radio-frequency amplifier 4 and an aerial 5 foramplifying and transmitting signals provided by modulator 2. A receivingsection of the interface device (I1) comprises, apart from aerial 5, asuperheterodyne receiver connected to the aerial, with a radio-frequencyamplifier 6, a mixer 7, an intermediate frequency stage 9 and ademodulator 10. A local oscillator 8 is connected to mixer 7 and has aninput connected to a programming device, in particular a dip-switch 30that is typically programmed at the time of installation in the machine.A decoder 11 is connected between the superheterodyne receiver and, bymeans of a constant delay generator 12, to the logic unit 1 and has aninput connected to the numerical control N1. A second decoder 13 isconnected to the demodulator 10 and the numerical control N1.

Electric circuits, located in each probe, are schematically shown inFIG. 3 where they have been divided in four sections: a transmittersection 35, a receiver section 36, a logic section 37 and a power supplysection 39.

The transmitter section 35 comprises a modulator 25, connected to aradio-frequency oscillator 27, the oscillation frequency of which isdetermined by signals arriving from programming devices, in particular adip-switch, 29, that are typically programmed at the time ofinstallation of the probe in the machine.

In the illustrated example, an identical frequency is assigned to allthe probes on the same machine, while different frequencies are assignedto the probes on other machines (M1, M2, M3). In the same manner thedevices 30 of the interface devices (I1, I2, I3) on each of the variousmachines are programmed.

A radio-frequency amplifier 28 is connected to modulator 25 and pilotsan aerial 14.

The receiver section 36, connected to aerial 14, comprises, in sequence,a radio-frequency amplifier 15 with selective characteristics, ademodulator 16, a band-pass filter 17 tuned at the modulation frequencyof the activation and enable signals, a low frequency amplifier 18, asignal detector 19, and a gate 23.

The logic section 37 comprises a decoder 21, for decoding the activationand enable signals, connected to the output of the low frequencyamplifier 18, and a logic control unit 22, connected to decoder 21 andthe programming devices 29, from which it receives the probe selectionsignals that are typically programmed at the time of installation in themachine.

A coder 26 for the identification signals is connected to the logic unit22 and the devices 29, from which it receives the signals for theselection of the probe. Probe switch means 38 are connected to a coder33 for determining the condition of the probe and that of a battery 24(coder 33 also receives information from battery 24, referred tohereinafter).

A switch 34, controlled by logic unit 22, alternatively connects thecoders 26 and 33 to modulator 25 in the transmitter section 35.

The power supply section 39 comprises power supply means with battery24, switching means, with a switch 40 that connects battery 24 toreceiver section 36, an oscillator circuit 42 (connected to the battery)and a gate 41. Gate 41 is connected to switch 40 for controlling thepower supply of the receiver section 36 on the basis of the signalsreceived from oscillator 42, signal detector 19 and logic unit 22.Furthermore, the power supply section 39 comprises second switchingmeans, with a second switch 20 for connecting battery 24 to logicsection 37. Gate 23 is connected to switch 20 for controlling the powersupply of the logic section 37 on the basis of the signals received fromsignal detector 19 or from logic unit 22. Further switching means,including a third switch 31 connected to logic unit 22, that controlsits state, control the power supply of the transmitter section 35.

In the diagram shown in FIG. 4, the logic blocks identify the followingfunctions:

block 50--starting of the procedure for the activating of a probe (forexample, S1a) on a specific machine (for example, M1);

block 51--test relating to the sending, or non sending, of a signal forthe starting of the procedure from the machine numerical control (N1) tothe inherent interface device (I1);

block 52--generating and sending, by the interface device (I1), of ageneric activation signal AT;

block 53--activating, subsequently to receiving the signal AT, of aspecific number of probes, in particular the probes that are within theoperating range of aerial 5;

block 54--sending of an identification signal ID, at a random instantwithin a determined time interval, by each of the activated probes;

block 55--test relating to the identification signals ID received by theinterface device I1;

block 56--test relating to the time elapsed after the sending of theactivation signal AT;

block 57--test relating to the time (τ) that has elapsed after theinterface device I1 has received the identification signal ID sent bythe probe S1a selected for activation;

block 58--generating and sending, by the interface device I1, of ageneric confirmation, or enable signal, EN;

block 59--test relating to the reception of EN by the activated probes;

block 60--change in the power supply state of some probes;

block 61--test relating to the number of inspections performed;

block 62--performing of the control cycle by the selected probe S1a, onthe basis of the instructions provided by the associated numeric controlN1;

block 63--test relating to the activating time of the selected probeS1a;

block 64--change in the power supply state of the selected probe S1a;

block 65--ending of the procedure.

FIG. 5 schematically shows the signals transmitted by one of theinterface devices (I1) and by some probes.

The system operation is now described, firstly from a logic point ofview, and thereafter with reference to the block diagrams in FIGS. 2 and3.

In the working environment, schematically shown in FIG. 1, all theprobes on all the machine tools are in a standby, low-power state andonly some of the circuits of each probe are powered.

The procedure for activating--on machine M1--a selected probe, forexample probe S1a, for performing a checking cycle on that machine M1and maintaining the other probes on the same or on other machines in astand-by state is the following:

The numeric control N1 sends an appropriate signal for the starting ofthe procedure to interface device I1 (block 51), that generates andtransmits a generic activation signal AT (block 52).

Signal AT causes the energizing, in other terms the high-power state ofa part of the probes (for example probes S1a, S1b, S1c, S1d, S2a), i.e.the probes within the operating range of interface device I1 (block 53).Each activated probe generates and sends, within a predetermined timeinterval (Ta, Tb, Tc, Td) an identification signal ID (block 54).

The instant at which the transmission of each of the identificationsignals ID starts is of random type and is evenly distributed within theassociated time interval.

The interface device I1 detects the reception of the identificationsignal ID of the selected probe (S1a) on the basis of thecharacteristics of the signal ID (block 55). If the interface device I1does not detect the reception of the aforementioned signal ID within apredetermined time limit, the procedure starts again from the beginning(block 56).

At the-reception of the proper ID signal and subsequently to a prefixedtime delay τ (block 57), the interface device I1 sends a generic enablesignal EN (block 58).

The probes that have not received the enable signal EN within a timedelay τ from the instant at which they transmitted their associatedidentification signals ID, de-energize and return to the stand-by state(blocks 59, 60).

Conversly, the probes that receive the enable signal EN within theformerly mentioned time delay τ (from the instant at which theytransmitted their associated identification signals ID), re-send theiridentification signals ID at random moments within a subsequent,predetermined time interval Tx, and the previously described steps(blocks 54-60) are repeated.

These steps are repeated for other times: in the illustrated exampletwice, by sending identification signals ID in time periods Ty and Tz.At the end of the activation procedure (block 61) the selected probeS1a, that after every transmission of the identification signal ID hasalways received an enable signal EN, subsequently to the time delay τ,is thus activated and sends signals relating to the condition of theprobe and the battery (identified by number 24, in FIG. 3), so startingthe actual checking cycle. Probe S1a is automatically deactivated(blocks 63, 64) after a time period counted starting from the activatingof probe S1a, or from an operating phase of probe S1a (for example fromthe last monitoring of a state variation).

As the instant of transmission of the identification signal ID (within apredetermined time period) is of random type and the ID signals havedifferent characteristics, it is extremely unlikely that several probesbe accidentally activated. Even if a similar condition is quiteimprobable, there is a chance it may occur at the beginning of theactivation procedure to probes on different machines, for example,subsequently to the first sending of the enable signal EN, as shown inFIG. 5. However, additional exchanges of identification signals ID (onlyfrom the active probes) and enable signals EN permit to improve theselecting of just the probe (S1a) that it is actually required toactivate. Obviously, the probability that undesired activations occur isreduced further the greater is the number of enable signals EN requiredfor ending the procedure (block 61).

In the example shown in FIG. 5, the transmissions of identificationsignals ID from probes S1a and S2a, subsequently to the reception of theinitial AT signal, are substantially simultaneous. The enable signal ENis received by both probes S1a and S2a after the elapsing of time τ andthus both remain activated, and transmit associated identificationsignals ID at random moments within the following interval Tx.

However, in this case the ID signals sent by S1a and S2a occur atdistinct moments: the interface device I1 ignores the ID signal of probeS2a (owing to the fact that its frequency indicates that it comes from adifferent machine, M2), and as the latter does not receive the enablesignal EN at the appropriate time period (after delay τ), it isde-activated and returns to the stand-by state.

It is practically impossible to activate a probe by the previouslydescribed activation procedure, without considering the identificationsignals ID transmitted by the probe. Thus, it is extremely improbablethat noise can activate a probe.

With reference to the block diagrams shown in FIGS. 2 and 3, the systemoperates in the following way.

When the system is in a stand-by state, within the circuits of eachprobe (FIG. 3) the transmitter section 35 and the logic section 37 arede-activated (switches 20 and 31 open). As the receiver section 36 hasnot received any signals, it is powered, through switch 40, with pulsesgenerated by oscillator 42 and sent to gate 41. The presence of theoscillator 42 (that has negligible consumption) enables to minimize theenergy consumption by the probe in the stand-by state. According to atypical embodiment, the pulses emitted by oscillator 42 last 5 msec andoccur at 50 msec intervals from each other, hence permitting to reducethe average energy consumption of the receiver section 36 (and thus inthe stand-by state that of the entire probe) by about 90%.

When the numerical control N1 sends a start signal to logic unit 1 ofthe interface device I1 (FIG. 2), unit 1 generates a generic activationsignal AT. The radio-frequency carrier generated by oscillator 3 (whichis the same for the different interface devices I1, 12, 13) ismodulated, in modulator 2, by the activation signal AT, and thenamplified (4). The resulting signal is irradiated by aerial 5 andcaptured by the aerial 14 of each probe that is within the range of theaerial 5. The received signal is amplified (15), demodulated (16),filtered (17) and amplified again (18) for each probe. The signal(typically lasting 100 msec) is sent to detector 19, that, as aconsequence, keeps the switch 40 closed (by means of gate 41) and, bymeans of gate 23, causes the closure of switch 20 that connects thebattery 24 to the logic section 37.

The decoder 21 identifies the activation signal AT and sends a suitablesignal to the logic control unit 22, that sends signals to switch 40(through gate 41) and to switch 20 (through gate 23) for keeping thereceiver section 36 and the logic section 37 powered. Furthermore, logicunit 22 sends an enable signal to switch 34 for connecting the coder 26of identification signals ID to modulator 25 of the transmitter section35. Moreover, logic unit 22 power supplies the transmitter unit 35 (bymeans of switch 31) just for the time necessary for the transmission ofidentification signals ID, in order to avoid interferring with thereception of subsequent enable signals EN.

Furthermore, the logic unit 22 defines, on the basis of the signalsarriving from devices 29, the transmission time intervals (Ta, Tb, . . .) and, within these time intervals, the random instants at which theidentification signals ID are transmitted. Unit 22 has the additionaltask of checking that the enable signals EN are being receivedsubsequently to the requested delay time τ from the transmitting ofidentification signals ID. If an enable signal EN is not receivedsubsequently to time delay τ, unit 22 stops the energizing of thevarious sections and brings the probe circuits back to a stand-bycondition.

The identification signals ID are sent to modulate (25) the carriergenerated by the radio-frequency oscillator 27. The frequency of thelatter oscillator--that may be a specific characteristic of the machineon which the probe is installed--is defined by signals arriving from theprogramming devices 29. The modulated signal is then amplified (28),irradiated by aerial 14, received by aerial 5 and processed by thesuperheterodyne receiver of the interface device I1 (blocks 6, 7, 8, 9,10). The frequency of the local oscillator 8 is defined by signalsarriving from the programming device 30. If these latter signalsrepresent the same radio-frequency channel set on the transmittersection 35 of the probe and defined by devices 29, at the output of thedemodulator 10 there is present identification signal ID, that is sentto decoder 11. On the basis of the indications provided to the decoder11 by the numeric control N1 and relating to the probe S1a that it isdesired to activate, a check is made to ascertain whether the receivedsignal ID has been transmitted by the selected probe S1a. In theaffirmative, block 11 sends a signal that--after delay τ (12)--causesthe generating by block 1 of a generic enable signal EN that modulatesthe carrier generated by the radio-frequency oscillator 3. The signalsupplied after the subsequent amplification (4) is irradiated by aerial5.

When the interface device I1 is receiving, block 1 keeps theradio-frequency oscillator 3 off in order to avoid interferences.

The signal irradiated by aerial 5 is received by the aerial 14 of eachprobe that is within the range of aerial 5. The received signal isrecognized by decoder 21 as the enable signal EN, and the logic unit 22checks to see that the signal has been received within the time delay τfrom the transmission of the identification signal ID, and in this caseit is interpreted as a reply by the interface device I1 to theidentification signal ID transmitted by the probe. A new identificationsignal ID is generated (26) and sent by means of the transmitter section35.

Once the procedure for activating the selected probe (for example, probeS1a) has been successfully accomplished, after receiving a sufficientnumber of enable signals EN, logic control unit 22 maintains thetransmitter section 35 powered and, by means of switch 34, connectscoder 33, relevant to signals arriving from the probe among which thesignals monitoring the state of the probe and the battery, to modulator25 of the transmitter section 35, thus commencing the normaltransmission.

On the basis of the signals received by interface I1, through aerial 5,the signals monitoring the state of the probe and that of the batteryare sent, by means of decoder 13, to numeric control N1.

The de-activating of the circuits in the probe (S1a), in other terms thereturning to the stand-by state, occurs when the time set in a timerinside unit 22 elapses. According to a typical embodiment of thehereindescribed system:

the activation signal AT is made up by the emitting of a radio-frequencycarrier modulated at 10 KHZ for approximately 100 msec;

the intervals Ta, Tb, Tc, Td, Tx, Ty, Tz last approximately 128 msec andoccur at 20 msec intervals from one another;

the identification signals ID are supplied by modulating aradio-frequency carrier with serial sequences of bits at 10 Kbit/secfrequency and with complete signal duration time of about 5 msec;

the characteristics of the enable signals EN are similar to those of theactivation signal AT, apart from the duration that is of about 11 msec;

time τ is of approximately 20 msec.

According to a possible embodiment, differing slightly from theprocedure described with reference to FIG. 5, the probes, that--whenactivated by the initial signal AT--receive an enable signal EN beforetransmitting their identification signals ID, are de-activated (in otherterms return to the stand-by state) by the enable signal EN (in theexample shown in FIG. 5, the probes S1b, S1c and S1d, activated by AT,would be in that case de-activated by EN). The reasons and the practicaladvantages offered by this different embodiment appear evident by thepreviously described logic of operation. The extremely schematic andlinear procedure, shown in FIG. 5, has been illustrated for the purposeof providing simplicity and clarity to the description.

The previously described method relating to a radio-frequencytransmitting system can be employed even in the case of other wirelesssignals, for example of optical type.

The invention can be applied, for example, in the following cases:

a plurality of coordinate measuring machines in a single workingenvironment, or machine tools and/or measuring machines equipped withchecking probes;

just a single machine tool or measuring machine, with a plurality ofchecking probes;

coordinate measuring machines with or without numeric control;

the above cases, in which the checking probes are contact detectingprobes, and/or measuring probes comprising detecting devices withtransducer means.

What is claimed is:
 1. A system comprisinga plurality of assemblieswithchecking probes, detecting devices, transmitting devices forgenerating and wireless sending identification signals, receivingdevices for the wireless reception of an activation signal foractivating the assemblies, a power supply, and a switch for providing aconnection between the power supply and the transmitting devices, and acontrol unit, physically remote from the assemblies, for generating andtransmitting said activation signal, for receiving the identificationsignals, and for generating and transmitting to the assemblies aconfirmation signal, wherein said receiving devices can receive saidconfirmation signal, and wherein one of said transmitting devices ofeach checking probe defines a corresponding time interval, and saididentification signal of a preselected probe is transmitted within thecorresponding defined time interval to the control unit; and wherein,upon reception of said identification signal, said control unitgenerates and transmits said confirmation signal.
 2. A system accordingto claim 1, wherein the receiving devices of the probes comprise timersfor controlling said switch to inhibit the connection between the powersupply and the transmitting devices.
 3. A system according to claim 2,wherein the probes are contact detecting probes, and the control unitincludes a constant delay generator for transmitting said confirmationsignal after a predetermined delay (τ) from the receiving of apredetermined identification signal.
 4. A system according to one of thepreceding claims, wherein the transmitting devices are radio-frequencytransmitting devices and the receiving devices are radio-frequencyreceiving devices.
 5. A system comprisingat least a contact detectingprobe with detecting devices for detecting the contact between the probeand a workpiece to be checked, a power supply battery, transmittingdevices for the wireless transmission of signals, a switch forconnecting and disconnecting the battery to said transmitting devices,and receiving devices, connected to the switch, for receiving a wirelessactivation signal and controlling the connection between the battery andsaid transmitting devices, and at least a control unit, physicallyremote from the probe, and adapted for transmitting said activationsignal, characterized in that the switch contains a controller forautomatically connecting and disconnecting the battery to the receivingdevices, wherein the transmitting devices are radio-frequencytransmitting devices and the receiving devices are radio-frequencyreceiving devices.
 6. A system according to claim 5, wherein saidcontroller of the switch comprises an oscillator circuit.
 7. A methodfor controlling the activation of a remote assembly by a control unit ina system with at least one control unit and a plurality of assemblies,physically remote from the control unit and each assembly comprising aprobe, a power supply, detecting devices, receiving devices andtransmitting devices for receiving and transmitting wireless signals,the method comprising the following steps:generating and sending anactivation signal by the control unit, receiving said activation signalby the receiving devices of at least a part of said plurality ofassemblies, temporary energizing the assemblies of said selected partupon receipt of said activation signal, sending, by the transmittingdevices of the assemblies belonging to said part, associatedidentification signals at instants subsequent to said temporaryenergizing, receiving the identification signals by the control unit,sending, by the control unit, a confirmation signal upon reception ofone of the identification signals, and interrupting the temporaryenergizing of each assembly that does not receive the confirmationsignal subsequently to the sending of the associated identificationsignal, characterized in that the step of sending identification signalsoccurs, for each assembly of said part, within a predetermined timeinterval, and the confirmation signal is sent upon reception of theidentification signal of a preselected assembly within the correspondingpredetermined time interval.
 8. The method according to claim 7, whereinthe step of sending identification signals takes place, for eachassembly of said part, at a random moment within said predetermined timeinterval.
 9. The method according to claim 8, wherein the step ofsending, by the control unit, the confirmation signal occurs after apredetermined time delay (τ) from the reception of the identificationsignal of the selected assembly.
 10. A method according to one of claimsfrom 7 to 9, for controlling the activation of a selected probe in asystem with a numeric control machine comprising said plurality ofassemblies, wherein the predetermined time intervals are distinct fromone another.
 11. A method according to one of the claims from 7 to 10,for controlling the activation of a selected probe in a system with aplurality of numeric control machines carrying said plurality ofassemblies, wherein an identification signal transmitted by one of theassemblies of said part has a characteristic relating to the machinethat carries the assembly.
 12. A method according to claim 11, whereinthe step of receiving the identification signals by the control unitcomprises the identification, by the control unit, of saidcharacteristic.
 13. A method according to claim 12, wherein saidcharacteristic is a transmission frequency.
 14. A method according toone of claims 7 to 9, wherein said wireless signals are radio-frequencymodulated signals.
 15. A method according to one of claims from 7 to 10,wherein said wireless signals are optical signals.